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Topic: Solderless LED Matrix? (Read 5558 times) previous topic - next topic

Pedro147

#15
Oct 28, 2012, 10:25 am Last Edit: Oct 28, 2012, 01:15 pm by Pedro147 Reason: 1
Thanks for the encouragement Docedison.

Yes as you may have noticed I am finding the coding side of things a steep learning curve whereas some beginners on the forum seem to pick it up rather quickly :smiley-mr-green: Oh well I will keep plodding along and yes I am having fun and that's the main thing,

Pedro.
http://www.pedroduino.com

CrossRoads

Yup, I get  a lot of use out of the pololu.com wires & headers & stuff.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

dtaylorl

I guess the reason I just want to control individuals LEDs is that I don't have the wires, etc. yet to make my matrix, but I do have enough to plug in 8 LEDs and start experimenting with them. I'm hoping to be able to learn about the Max this way as I wait for the other parts to arrive.

dtaylorl

Can someone help me understand how the matrix works? I've wired up a 3x3 matrix as in the attached image (no Max chip at this point). My understanding is that if I apply 3.3 volts to row C and make column 1 ground, the electricity should flow through the bottom-left LED (as in the top-right of the image), turning it on. What seems to be happening, though, is that the electricity bypasses the LED and flows directly to the ground, meaning no LEDs light up (as in the bottom part of the image). This makes sense to me since electricity usually follows the path of least resistance. But everything I am reading online seems to indicate that what I am trying should light up the LED. What am I missing here? Can anyone help me out?

I should also note that I have a 100 ohm resistor at the beginning of each row.

CrossRoads

If you measure from C to 1, do you measure a short?
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

Aaron_dyer

Pedro,

I love your 8 x 8...

could you attach your code for that please.....that was pretty cool

Aaron_dyer


Quote


That is a ridiculous price for the MAX7219. Well, the normal price is the ridiculous one...but $1.25 is unheard of. Somehow I think that can't last long.


FYI, I bought some from Ebay...10 for 4.99 $  2 weeks waiting time but oh well

http://www.ebay.com/itm/130733916831?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

CrossRoads

Yes, still $1.25 for MAX7219 DIPs. Just ordered 12 more, $1.80 for shipping.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

Aaron_dyer

I'm patient though...I can wait a few weeks because I have LED flex strips as well coming....another Nano coming as well......lots of projects.....

I'm going to shorten another enclosure down to just two matrices and make sure I get it scrolling how I would like too....

I have 1 max7219 left...10 on the way....

I'm looking into maybe getting some larger matrices too, maybe some RGB's

Pedro147

Aaron, glad you like my 8 x 8 displays. When I get home from work I will post the code. Good luck with your 8 x 32 enclosure, I am also working on one. The Max 7219 chips are very popular on the forum lately aren't they.
http://www.pedroduino.com

dtaylorl


If you measure from C to 1, do you measure a short?

How would I go about testing this? If I do measure a short, what problem might this indicate?

CrossRoads

Use a digital voltmeter.
If it measures shorted, you need to find & remove the short.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

CrossRoads

Pedro, you can click Additional Options below and attach it right here, no need for outside links.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

Pedro147

Thanks for that Crossroads

Aaron, here is  the code for the 8 x 8 display patterns in reply  13

Pedro.
http://www.pedroduino.com

Aaron_dyer

Sweet! Thanks Pedro. Oh and while I have you ans crossroads, my 8 x 32 is ......75% working......at first I had letters backwards and was looking at the code for the problem, but then I woke up and realized my column pin outs were swapped.....so the matrices are good on correct letters now, its just my code somehow makes all 4 say the same letter from my string as they each scroll.....I want them to scroll across one another......still WIP

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